Directional antenna



March 29, 1938. P. s. CARTER DIRECTIONAL ANTENNA Filed NOV. 13, 1956 tmv III"

INVENTOR PHILIP 5. CARTER BY v ,um

ATTORNEY Patented Mar. 29, 1938 PATENT OFFICE DIRECTIONAL ANTENNA nPhilip S. C'arter, Port Jeierson, N. Y., assigner to Radio Corporationof America, a. corpora tion of Delaware Application November 13, 1936,Serial No. 110,599 9 claims. (C1. 25o-11) This invention relates to-adirectional antenna system, and more particularly to such a systemwherein there are employed a plurality of individual radiating elementsso arranged that the currents therein bear a desired phase relation withrespect to one another.

In the transmission of horizontally polarized Waves, it has heretoforebeen proposed to employ a plurality of half wavelength, approximatelyhorizontal radiating elements arranged in substantially the samestraight line and disposed vertically approximately one-half wavelengthfrom a similarly arranged group of half wavelength radiating elements,and so energized that the direction of lradiation is perpendicular tothe axis of the radiating elements. In such known arrangements, theapproximately one-half wavelength vertical spacing between the twogroups of radiators was necessary in order toprovide desired cophasalrelationship of the currents in all the radiating elements. Adisadvantage of this type of antenna is the fact that there is required,for its proper mechanical construction, a catenary arrangement whichenables the individual radiating elements of each group or tier to bealigned in the same straight line, at a constant vertical spacingbetween adjacent tiers. Another disadvantage lies in the absence of anyprovision for adjusting the phase relation of the currents in the wires.In practice, some adjustment is always necessary to obtain ythe desireddirectional effect, since it is difficult, if not almost impossible, todetermine the effects upon the phase relations of the currents, of suchiactorsasinsulators, and the looping and bending of the feederwires'between adjacent radiating elements of the same group. A furtherdisadvantage of the known antenna systemfdescribed above lies in thenecessity of providing an approximately one-half wavelength verticalspacing between groups of one-half Wavelength radiating elements lyingsubstantially along dierent axes.

The foregoing disadvantages arer overcome in accordance with the presentinvention which provides a highly directional antenna of the typedescribed above, but which is not limited toany one particularv value ofspacing betweenadjacent groups of radiators, and which provides forproper adjustment of the phase relations between currents in theradiators of each group. A detailed description of the invention,accom.- panied by-a drawing follows:

Referring to the single figure of the drawing, there is shownfalbroadside antenna system vfor radiating horizontally polarized waves,comprising two groups of substantially half wavelength radiatingelements I, I and 2, 2 suitably supported between poles P, P. Eachradiating element I and 2 is electrically'separated from its adjacentelement, extending generally along the same axis, by an insulator hereindesignated X, although adjacent radiating elements are electricallycoupled together through vertical interconnecting wires 3, 4, whichextend between groups I, I and 2, 2.

For energizing the antenna system, there is provided a suitabletransmitting circuit, herein conventionally shown in box form 5, whichis connected over transmission line TL and through a suitable impedancematching circuit 6 to the center points of the middle pair of verticalinterconnecting wires 3', 4. The connection of the transmission line TLto the center points of the middle wires 3, 4 insures the cophasalexcitation of the rlrst two radiators in each group to which thevertical wires are directly connected. For achieving cophasal excitationin adjacent radiating elements 2, 2 and I, I of each group of radiators,there are provided across the interconnecting wires 3, 4 a pair ofconducting strips 1 and 8 which can be adjusted over the lengths of thewires 3, 4. Strips l and 8 are symmetrically located With respect to thecenters of the interconnecting wires 3, 4. In this manner, by suitableadjustment of the strips, there is obtained cophasal energization in theradiating elements, and out of phase energization in `those portions ofthe wires 3, 4 which extend from the stripI to their associatedradiators. When `the wires are perfectly tuned, the strips 'I and 8 willbe located at a voltage nodal point for the energy in the wires. Thecurrent distribution throughout the radiating elements of theinterconnecting wires are shown by dotted lines, and the" arrowsindicate the direction of the instantaneous current How in the radiatorsand wires. It will thus be observed that there is substantially completecancellation of radiation from' the interconnecting wires 3, 4, althoughaddition of radiation from the radiating elements I, I and Due to thefact that the voltages on the strips 'I and 8 are a minimum and equal invalue, it is4 possible to connect the conducting strips together throughthe intermediate portions' of `the interconnecting wires 3, 4 withoutthe use of` insulators, thus achieving another advantage over priorarrangements wherein additional insulators` are necessary at theequivalent ofthis location to prevent direct contact between adjacentcrossconnecting feeder wires.

Because of the fact that the strips 'I and 8 are adjustable over thelengths of the Wires 3, 4, it is possible to overcome variousirregularities in the system and thus obtain the desired currents andphase relations in the radiators. Also, by adjusting strips 'I and 8,the antenna can be made to accommodate a considerable range offrequencies, in which case the radiating elements I, I and 2, 2 maydepart from an exact ha wavelength.. l

It should be noted that although the radiator of each group I, I and 2,2 are substantially, more or less so, in the same line, there is adeparture from this straight line due to mechanical considerations. Forthis reason the spacing between the two groups of radiators I, I and 2,2 is not constant, and varies from maximum spacing at the points ofsuspension at the poles'P',

to a `minimum spacing at the center of the span between the poles. Inthis way the wires themselves form a sort of catenary, whereas`heretofore, in priorV arrangements, it has always been necessary toprovide a separate catenary from which the antenna elements weresuspended.

`It will thus be obvious, from an inspection of the drawing and what hasbeen said before, that the minimum spacing between groups ofradiators I,I and 2, 2 should not be substantially less than one-half wavelength,since it is desired that the overall length of path from the adjacentends of any two radiators in the same group, as measured along wires 3and 4 and through its associated strip, be in electrical effect,equivalent to one-half Wavelength, in order that the phase relations bethe same in the adjacent radiating elements. It is preferred, however,that the mean or average spacing between the groups f ,i of radiators I,I and 2, 2 be greater than onehalf wavelength for two purposes. First,in order to give the strips l and 8 a degree of adjustability overthewires 3, 4, for accommodating a range of frequencies, and secondly,because I have found that the mean spacing which will give the maximumpower `gain for the arrangement shown in the drawing of the two groupsof radiators is about 'lths .of a wavelength. Such a spacing will,theoretically, give'a power gain of three to one over a single group ofelements, whereas a half wavelength spacing between groups of radiatorswill give a power gain of only slightly more than two to one, ascompared to a single group of radiating elements.

Although the antenna of the invention has been described especially inregard to a transmitter, it willbe understood, of course, that it is notlimited thereto but it may be applied as well to receiving arrangements,and that, if desired, reflectors maybe employed at suitable distances inthe rear of the antenna. Such reflectors may have the identical form ofthe antenna of the invention, or be of any other desired configuration.Similarly, the reflector may be directly energized'or parasiticallyexcited (floating). It should also be understood that the invention isnot limited to any particular number of elements in any one group, sincea greater or less number than that shownk might be employed between anytwo poles. Moreover, the features of the invention are not limited to ahorizontal antenna. for the transmission of horizontally polarized wavessince, where desired, a vertical antenna employing the invention mayalso be used, in which case the radiatingelements I;

I and 2, 2, and the strips I and 8 would be vertically disposed whilethe interconnecting wires 3, 4 and 3', 4 would be horizontally disposed.Occasions may also arise where it is desired to use a polarization whichis not strictly vertical or horizontal but is at some desired angle, inwhich case the antenna of the invention may be disposed at any angle tothe horizontal or vertical, without departing from the spirit and scopeof the appended claims.

What is claimed is:

l. An antenna system comprising two radiating elements,` eachsubstantially one-half the length of the communication wave and disposedin substantially the same straight line, two other similar radiatingelements disposed substantially in a line parallel tosaid first twoelements, a pair of interconnecting Wires disposed substantially at aright angle to said first two pair of radiating elements and connectingthe adjacent ends of said first two radiating elements to the adjacentends of said second two radiating'elements, and means connected acrossand adjustable along the lengths of said pair of interconnecting wiresfor adjusting thecurrent and phase relations in said radiating elements.

2. An antenna in accordance with claim l, characterized in this thatsaid means comprise two electrical conductors substantiallysymmetrically disposed with respect to the center of saidinterconnecting wires.

3. An antenna comprising a plurality of linear radiating elements in theform of a line supported at both ends from a pair of vertical supportingstructures, another group of radiating elements similarly arranged andsupported between said structures and spaced away from said first group,an insulator between adjacent radiating elements of each group, a pairof interconnecting wires connecting the adjacent ends of the radiatingelements in one group with the correspond-` ingly located adjacent endsof the radiating elements of the other group, and a pair of conductingstrips connected across and adjustable along the lengths of each pair ofinterconnecting wires for adjusting the current and phase in saidradiating elements.

,v 4. An antenna in accordance with claim 3, characterized in this thatthe two groups of radiating elements are substantially horizontal and inthe form of catenaries, the average spacing between said two lines ofYelements being greater than one-half the length of the communicationwave. v

5. AnA antennaA comprising a plurality of linear radiating elements inthe form of a line supported at both ends from a pair of verticalsupporting structures, another group of radiating elementssimilarlyarranged and supported between said structures and spaced awayfrom said rst group, an insulator between adjacent radiating elements ofeachv group, a pair of interconnecting wires connecting the adjacentends of the radiating elements in one group with the correspondinglylocated adjacent ends of the radiating. elementsv of theother group, anda pair of conducting'strips connected across each pair ofinterconnecting wires for adjusting the current and phase ini saidradiating elements, said two lines. offradiatingv elements beingsubstantially horizontal and in the form of catenaries, the averagespacing between said two lines being substantially seven-tenths ofthelength of the communication wave.

6. An antenna comprising a4 plurality of linear arrangement locatedbetween each of said iirstl radiating elements in the form of a linesupported at both ends from a pair of vertical supporting structures,another group of radiating elements similarly arranged and supportedbetween said structures and spaced away from said rst group, aninsulator between adjacent radiating elements of each group, a pair ofinterconnecting wires connecting the adjacent ends of the radiatingelements in one group with the correspondingly located adjacent ends ofthe radiating elements of the other group, and a pair of conductingstrips connected across each pair of interconnecting wires for adjustingthe current and phase in said radiating elements, said two lines ofradiating elements being substantially horizontal and in the form ofcatenaries, the average spacing between said two lines being' greaterthan one-half the length of the communication wave, said catenarieshaving opposite curvatures.

7. An antenna system comprising two radiating elements, eachsubstantially one-half the length of the communication wave and disposedin substantially the same straight line, two other similar radiatingelements disposed substantially in a line parallel to said iirst twoelements, a pair of interconnecting wires disposed substantially at aright angle to said first two pair of radiating elements and connectingthe adjacent ends of said rst two radiating elements to the adjacentends of said second two radiating elements', means connected across saidpair of interconnecting wires for adjusting the current and phaserelations in said radiating elements, another similar arrangement offour radiating elements similarly coupled together and arranged insubstantially the same plane as said first four radiating elements, eachline of radiating elements in said iirst arrangement having asubstantial continuation of said line in said second arrangement, asupporting structure between said two arrangements of radiatingelements, another pair of interconnecting wires disposed substantiallyat a right angle to said two lines of radiating elements and connecting'together the ends of the elements of each arrangement nearest saidsupporting structure, and high frequency apparatus coupled to the centerpoints of said last pair of interconnecting wires.

8. An antenna system comprising rst, second and third successivelyspaced supporting structures, said rst and third structures beingequally spaced from said second structure, an antenna and thirdstructures and said second structure, said antenna arrangements being inthe same plane, similarly constructed, and supported at the same heightabove ground from said structures, each of said antenna arrangementscomprising two groups of substantially horizontal radiating elements inthe form of catenaries, said catenaries of each antenna being separatedfrom each other an average vertical distance greater than one-half thelength of the communication wave, each of said radiating elements beingapproximately one-half the length of the communication wave, and pairsof interconnecting wires disposed at substantially right angles to saidelements and connecting the adjacent ends of the elements of one groupto the adjacent ends of the correspondingly located elements of theother group in the same antenna arrangement, conducting strips connectedacross each pair of interconnecting wires for adjustingv the current andphase relations in their directly associated radiating elements, wherebyeach element in each group is coupled to the adjacent element of thesame group through said interconnecting wires and a strip, and highfrequency apparatus coupled to the radiating elements of both saidantenna arrangements which are nearest said second supporting structure.

9. An antenna comprising a plurality of linear radiating elements in theform of a line supported at both ends from a pair of vertical supportingstructures, another group of radiating elements similarly arranged andsupported between said structures and spaced away from said rst group,an insulator between adjacent radiating elements of each group, a pairof interconnecting wires connecting the adjacent ends of the radiatingelements in one group with the correspondingly located adjacent ends ofthe radiating elements" PHILIP S. CARTER.

